Battery state of charge not balanced.
I have 2 5kW ECO inverters and 5 x 5.32 Sunsynk battery packs.
Now I have connected Solar assist to the battery I have noticed that the batteries are not discharging together as I would expect.
Every day the PV fully charges all 5 packs (at least 99%) Later I notice that not all batteries are discharging at a similar rate. What is more confusing is that it appears random as to which battery packs are being utilised.
All the batteries use identical length DC cables to a busbar, then identical length DC cables from the busbar to inverter terminals so I don’t think this is an installation issue.
The battery software is identical on all 5 packs at P16S100A-E21390-1.08
This just does not sound right Here are some examples of the SOC a few hours after battery discharge starts.
Does anyone have any advice on this?
Thinking about your explanation. Your explanation is correct on how the to mosfets deal with handling charge and discharge currents. However to behavior is controlled by the MCU on the BMS and when using multiple batteries in parallel they use the comms connecting the batteries with one as a master and the other as slaves. This will then allow communicate with each other. This will then control the state of each BMS preventing the race condition that you have described.
If the comms is not working between the batteries, or they are not configured as Master/Slave, then you will see the behavior where the batteries will get out of balance.